Sink/washing machine waste to soil pipe - anti-syphon trap the trick

Following the big freeze, and having a narrow escape with a frozen
waste pipe going to an outside drain, I want to re-plumb the pipe to
go down the toilet stack in the cloakroom it passes, on it's way out
the wall.
I know you can get 90degree pan connectors with a fitting to accept a
waste pipe - so that side is sorted. However I am worried about
siphonage, when the toilet is flushed.
A lot of googling (why are plumbing matters so off-grid ?) and a phone
call to a local plumbers merchants suggests an anti-siphon trap
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do the job. The pipe run starts with the washing machine, and
goes about 6' before it's joined by the sink waste, and then will go
about 5' into the soil pipe.
Does this seem practical, sensible, and the correct way ? Presumably I
will need two (although the shop guy said one on the basin - the
washing machine wouldn't need one as it was so long ???????)
cheers guys.
Reply to
Jethro
Jethro ( snipped-for-privacy@googlemail.com) wibbled on Friday 21 January 2011 17:03:
Yes - you will get a strong suction effect when the loo is flushed, if a block of loopaper goes down (makes a most effective piston).
The trap you mentioned would be a good solution. It is likley the AAV integral to that trap will be sufficeint to protect the other trap, but I couldn't absolutely guarantee it. What's the seal depth on the other trap?
Another solution is to "roll your own" with a small AAV on a short vertical tee'd off pipe - perhaps near to the washing machine standpipe so the AAV could be put roughly as high as the top of the machine's standpipe thus abive the waterline of the basin.
A further solution would be to use a HepVO on the basin which will take care of everything.
Cheers
Tim
Reply to
Tim Watts
What an antisyphon trap does is let air into the pipework if a slight vacuum shows up. So there's not much need for 2 of them on one pipe.
I like keeping the drains as separate as they already are, that way if one ever blocks you do at least have the other.
NT
Reply to
Tabby
(Hits head with hand) Duh !!!! Of course ...
Well IMO the chances of the soil pipe blocking are much smaller than the chances of the waste pipe getting blocked (or frozen). And besides, the existing arrangement is aesthetically shit ... it comes out one side of the house, and goes all the way along (under the patio door) to the otherside ... a good 5m run.
Reply to
Jethro
(Hits head with hand) Duh !!!! Of course ...
Well IMO the chances of the soil pipe blocking are much smaller than the chances of the waste pipe getting blocked (or frozen). And besides, the existing arrangement is aesthetically shit ... it comes out one side of the house, and goes all the way along (under the patio door) to the otherside ... a good 5m run.
Just boss the waste pipes into the soil stack, you should have 3" seal traps on as the soil stack is vent to the atmosphere, there should be no problems witht the traps being pulled. No need for ati-vac traps.
Reply to
A Plumber

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